GEOTECHNICAL ENGINEERING ECG 503 LECTURE NOTE 12 4.0 GROUND IMPROVEMENT TECHNIQUES

LEARNING OUTCOMES Learning outcomes: At the end of this lecture/week the students would be able to: Understand natural slope and made engineered soil slope assessment which include rainfall induced failure and role of suction.

Hydraulic Methods and Objective of Vertical Drain and Preloading TOPIC TO BE COVERED Mechanical Methods and Objective; Stone Column, Dynamic Compaction, Vibrofloatation and Vibro Compaction. Physical and Chemical Methods and objective; Grouting and cement column Hydraulic Methods and Objective of Vertical Drain and Preloading

Vibrating Plates for compacting very small areas effective for granular soils

Smooth-wheeled Roller

Smooth Wheeled Roller Compacts effectively only to 200-300 mm; therefore, place the soil in shallow layers (lifts)

Sheepsfoot Roller to Compact Clay Soils

Sheepsfoot Roller Provides kneading action; “walks out” after compaction Very effective on clays

Impact Roller to Compact the Ground

Impact Roller Provides deeper (2-3m) compaction. e.g., air field

Dynamic Compaction - pounding the ground by a heavy weight Suitable for granular soils, land fills and karst terrain with sink holes. solution cavities in limestone Pounder (Tamper) Crater created by the impact (to be backfilled)

Pounder (Tamper) Mass = 5-30 tonne Drop = 10-30 m

Vibroflotation Suitable for granular soils Practiced in several forms: vibro–compaction stone columns vibro-replacement Vibroflot (vibrating unit) Length = 2 – 3 m Diameter = 0.3 – 0.5 m Mass = 2 tonnes (lowered into the ground and vibrated)

Vibroflotation

Vibroflotation

Blasting For densifying granular soils Aftermath of blasting Fireworks?

Earthmoving Equipment This is an Australian excavator, with height of a 3-storey building Large Excavator (see minivan on left for scale)

Grader for spreading soil

Bulldozer for spreading soil evenly

Loader

Backhoe

Crawler mounted Hydraulic Excavator

Rock Breaker

Filed Compaction Smooth-wheel roller Vibratory roller Different types of rollers (clockwise from right): Smooth-wheel roller Vibratory roller Pneumatic rubber tired roller Sheepsfoot roller

Big weights dropped from 25 m, compacting the ground. Craters formed in compaction

GENERAL BACKGROUND OF SOFT CLAY Malaysia Coastal Area – Not fully developed Soft clay usually located around the coastal area

The soft clay have been a source of difficulties for many years The soft clay have been a source of difficulties for many years. The soft soil can cause settlement which can give a lot of problem and damage in several way. This is the reason why Malaysia’s coastal areas are not generally developed

TWO DISTINCT ATOMIC STRUCTURAL UNITS 0.29 nm aluminium or magnesium hydroxyl or oxygen oxygen silicon 0.26 nm Silicon Tetrahedron Aluminium Octahedron

Micro-fabric particles in natural clay. Dispersed Flocculated

Flaky shape Plate like structure

ION EXCHANGE

Ground Improvements for Soft Clay Stone Column (Vibro-Replacement) Prefabricated Vertical Drain Cement Column

VIBRO-REPLACEMENT (STONE COLUMN)

Vibro-Replacement Also known as stone column. The technique are similar to vibroflotation/vibrocompaction except the granular fill materials which used is sand is replaced by gravel stone sizes ranging from 50mm to 100mm

Soil Layer Increase in density Increase in bearing capacity Radial drainage (help to improve settlement) Shear strength of soil improve Reinforcing the soil by applying rigid member (stone column) inside the soil

Stone Columns vibrator makes a hole in the weak ground hole backfilled ..and compacted Densely compacted stone column

PREFABRICATED VERTICAL DRAIN (PVD)

CEMENT COLUMN (CHEMICAL STABILIZATION)

APPLICATION OF STABILIZE CLAY

GROUTING TECHNIQUE

EXAMPLE OF CASE STUDY FOR GROUND IMPROVEMENT METHODS ON SOFT CLAY

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